The present invention relates to cleaners for cleaning the heads of devices reading from moving magnetic mediums and, more particularly, to a head cleaner for cleaning the heads of the floppy disc drive system.
A typical floppy disc, generally indicated as 10, is shown in FIG. 1 and in partially cut away enlarged view in FIG. 2. Disc 10 comprises a jacket 12 comprising opposed covering sheets 14 and 16 with a plastic disc 18 having magnetic surfaces 20 and 22 thereon disposed within the jacket 12 for rotation. The covering sheets 14, 16 of the jacket 12 are of a resiliently flexible material, as is the disc 18, thereby leading to the designation "floppy" disc. The jacket 12 is assembled with the disc 18 therebetween and then sealed about the edges as by folding sheet 16 over sheet 14 and sealing the two together in the area designated as 24 in a heat sealing process known in the trade as staking.
The disc 18 has a circular hole 26 in the center thereof. The covering sheets 14, 16 of the jacket 12 have circular holes 28 concentrically disposed with relation to the hole 26 and slightly larger than hole 26. In operation, the jacket 12 is inserted with one edge leading through a slot into the disc drive mechanism. When the mechanism is closed, the jacket 12 is retained therein and, simultaneously, a drive hub engages the circular hub hole 26 and grips the disc 18. The disc 18 is then rotated within the jacket 12 by the drive hub.
To provide for the reading and writing operations, a pair of opposed slots 30 and 32 are disposed in the jacket 12 through both covering sheets 14, 16 between the hub holes 26, 28 and one side of the jacket, labelled 34. Side 34 then becomes the leading side or edge which is inserted first into the disc drive mechanism. A pair of small opposed holes 36 are provided through the sheets 14, 16 adjacent the hub holes 26, 28. The disc 18 contains a small timing hole 38 therethrough. As the disc 18 rotates, the hole 38 passes between the holes 36 once in every revolution. Within the disc drive unit is a light source on one side of the disc 18 and a light sensing source on the opposite side. Each time the hole 38 passes between the holes 36, light is allowed to pass therethrough from the light source to the light sensing device. Thus, a positional timing signal is developed for use in determining the sector positions on the magnetic surfaces 20, 22 of the disc 18, as it rotates.
The floppy disc 10 can be used interchangebly in both one head and two head systems. This is shown in FIGS. 3 and 4, respectively. In a one head system, one head 40 moves through the slot 30 in and out in the direction of arrow 42. Simultaneously, a pressure pad 44 moves in and out in the direction of arrow 46. The pressure pad 44 has a felt pad 48 on the inner end thereof. When the locking mechanism of the disc drive is released so that the floppy disc 12 can be removed, the head 40 and pressure pad 44 move out of the slots 30, 32, respectively, to allow the floppy disc 10 to be withdrawn. When the disc 10 is inserted and the locking mechanism activated, the head 40 and pressure pad 44 move in through the slots 30, 32 to contact the magnetic surfaces 20, 22 of the disc 18. In this regard, the head 40 and pressure pad 44 act in much the same manner as the head and pressure pad of a cassette type tape system. The pressure pad 44 holds the magnetic surface 20 against the face of head 40 while the felt pad 48 slides smoothly over the magnetic surface 22.
In a two headed system such that of FIG. 4, a second head 50 is added, disposed on the opposite side of the disc 18 from the head 40. The first head 40 moves in and out in the direction of arrow 42 in the manner previously described with respect to FIG. 3. The head 50 moves in and out in the direction of arrow 52 in a similar manner.
With the earlier so-called "hard" disc drives, the heads floated over the magnetic surface of the disc on a thin film of air. Consequently, there was no contact between the head and the oxide material on the magnetic surface and, therefore, no transfer of the magnetic surface to the head. By contrast, the heads of a floppy disc system are prone to a build up of transferred magnetic material in the same manner as the heads of a cassette type tape system. Since a buildup of magnetic material on the face of the head can interfere with proper operation of the device, the heads must be kept clean. One alternative is to disassemble the mechanism and hand-clean the head with a rag and solvent. Such an approach is, however, not the optimal solution.
To solve this problem in cassette tape players, a cleaning device was provided by substituting an abrasive tape for the recording tape in the same type of cassette housing and drive mechanism. Such a device is shown in the German Pat. No. 2,301,533 to Polygram GmbH of Hamburg, Germany. The abrasive tape used is only mildly abrasive so as to wipe the oxide coating from the head surface without damaging the head. The tape is made of an absorbant material as well so that, additionally, the tape can be partially saturated with a suitable solvent such as isopropyl alcohol, or the like, to help in the cleaning process. In use, the tape of the cleaning cassette is partially moistened with solvent and then the cassette is inserted into the cassette player and operated in the normal manner. As the tape moves across the head, it wipes any oxide coating therefrom.
Adapting the above-described teaching method for cassettes to floppy disc drives was a simple and straightforward transition. Such a device is shown in cross section in FIG. 5 in the area corresponding to that of FIG. 2. As with the cassette system, substantially the same jacket 12 as for the floppy disc 10 comprising cover sheets 14, 16 and with openings 30, 32 therein is employed. In similar manner to the cassette system, the magnetic disc 18 is simply replaced with a cleaning disc 54 of the same resiliently flexible abrasive material, which is readily adaptable for rotation within the jacket 12 by the drive mechanism of the floppy disc drive in the same manner as the magnetic disc 18.
Such as approach worked adequately with the two head system of FIG. 4; but, with the one head system of FIG. 3, the abrasive cleaning disc 54 had an adverse effect on the felt pad 48 of the pressure pad 44 which was intended to slide on a smooth surface. Accordingly, a one headed cleaning disc was developed such as that shown in FIG. 6. The cleaning disc of FIG. 6 is representative of several patented designs including those of Allan (U.S. Pat. No. 4,180,840), Masuyama et al. (U.S. Pat. No. 4,106,067) and Sugisaki et al. (U.S. Pat. No. 4,065,798). In this dedicated single head cleaner, the same jacket 12 is one again used; however, in this case, a composite cleaning disc 56 is employed. One side of the disc comprises a cleaning disc 54' substantially identical to the cleaning disc 54 of FIG. 5, which is bonded to a disc of plastic material 58 or the like, over which the felt pad 48 is adapted to slide smoothly or the one side while the head is cleaned on the other side by the cleaning disc 54'.
Thus, it can be seen that the prior art cleaning disc of FIG. 5 is adapted for cleaning only a two headed disc system while the prior art cleaning disc of FIG. 6 is adapted for cleaning only a one headed system.
More recently, Davis, in U.S. Pat. No. 4,374,404, has patented the cleaning disc shown in simplified form in FIGS. 7 and 8, which is a partial solution to the problem. In the Davis approach, the simple cleaning disc 54 of FIG. 5 is employed and the jacket is modified. The jacket 12' uses one covering sheet 14' with an opening 30' therein. The opening 30' of the Davis apparatus is enlarged for other reasons which are the subject of another application. The opening 30' could be of the same shape as the opening 30 in the previously discussed embodiment. The opposed opening 32 in the opposite covering sheet 16' is filled with a perforated tab 60 at the time of manufacture, puchase, and delivery. At the time of use, if the Davis cleaning disc is to be employed in a one headed system such as that of FIG. 3, the perforated tab 60 is left in place and the pressure pad 44 and felt pad 48 thereof press against the tab 60 rather than the bottom surface of the cleaning disc 54. If the Davis cleaning disc is to be used in a two headed disc drive, the perforated tab 60 is removed to expose the full length of the slot opening 32 to the second head in the manner of FIG. 4. It will be appreciated that the cleaning disc of Davis can be used for single head unit cleaning and then be converted to two head unit cleaning; but, once the perforated tab 60 has been removed, the Davis cleaning disc is substantially identical to the prior art disc of FIG. 5 and, therefore, can no longer be used for a single headed system.
Wherefore, it is the object of the present invention to provide a cleaning disc for floppy disc drives which is simple in structure and which can be used interchangeably for one headed and two headed drives.